1. Technical Field
The present invention generally relates to vehicle suspension systems and more particularly to a semi-active anti-roll suspension system having a pair of independently mounted stabilizer bar halves which may be coupled to one another to control vehicle roll.
2. Discussion
Traditional vehicle suspension systems include resilient devices, such as coil springs and leaf springs, to flexibly support a portion of a vehicle and enable all of the wheels to maintain contract with the ground when traversing uneven terrain. Segregating the vehicle into unsprung and sprung portions in this manner is also useful for preventing severe impulsive forces from being transmitted to the vehicle occupants.
It is known that when vehicle travels around a corner, centrifugal forces acting on the vehicle tend to cause the sprung portion of the vehicle to roll. In severe instances, the effects of roll can cause instability and impede the ability of the driver to control the vehicle. Although the effects of roll are more pronounced with vehicles having a comparatively high center of gravity, such as vans or trucks, every vehicle is effected by roll.
In tuning the ride and handling of a vehicle, it is often desirable to soften or lower the spring rate of the suspension""s springs to provide a softer, less harsh ride. One of the main drawbacks associated with this approach is that a suspension system having springs with a relatively low spring rate permits the vehicle body to roll at a relatively higher rate. Accordingly, it would seem that the combination of springs with a very low spring rate and a relatively stiff stabilizer bar would optimize both the ride and handling of the vehicle.
The relatively stiff stabilizer bar, however, tends to directly connect the vehicle wheels such that the motion of one wheel is copied to another wheel. If a vehicle so equipped was to strike a bump with one wheel, for example, the upward force (i.e., jounce) imparted to that wheel would be transmitted through the stabilizer bar to the opposite wheel, causing the opposite wheel to move in an upward direction. This xe2x80x9ccross-talkxe2x80x9d between the vehicle wheels is highly undesirable as it adversely effects vehicle ride.
Another drawback of stabilizer bars is that their torsional stiffness inhibits the free travel of the vehicle wheels. Modern materials and design techniques have substantially reduced the weight of the vehicle wheels and mounting structures to such an extent that the weight of a wheel and its mounting structure is typically insufficient to cause the stabilizer bar to rotate. While this problem is rarely, if ever, noticed on the relatively flat surfaces of modern roads, it can become apparent when the vehicle is operated over un-even terrain. In some situations it is possible for one of the vehicle wheels to remain in an elevated position over a dip in the terrain due to the torsional resistance of the stabilizer bar. While situations of this severity are not routinely encountered, the fact remains that the stabilizer bar reduces vehicle traction in some situations.
Accordingly, there remains a need in the art for a suspension system having a stabilizer bar which reduces body roll while minimizing undesirable xe2x80x9ccross-talkxe2x80x9d between the vehicle wheels. There also remains a need in the art for a suspension system having a stabilizer bar which can be selectively controlled in a manner so that it does not affect vehicle traction.
In one form, the present invention provides a stabilizer bar assembly for a vehicle having a pair of laterally-spaced wheels. The stabilizer bar assembly includes first and second stabilizer bar members and a clutch assembly. Each of the first and second stabilizer bar members is coupled to one of the pair of laterally-spaced wheels. The clutch assembly is coupled to the first and second stabilizer bar members and is operable in a first condition and a second condition. Operation of the clutch assembly in the first condition permits the first and second stabilizer bar members to rotate independently of one another so as to the stabilizer bar assembly from copying the motion of one of the wheels to the other one of the wheels. Operation of the clutch assembly in a second condition couples the first and second stabilizer bar members for rotation with one another, so as to reduce vehicle body roll.